A three-dimensional shape measuring apparatus capable of acquiring information about the height of an inspection target portion is known in general. Such a three-dimensional shape measuring apparatus is disclosed in Japanese Patent Laying-Open No. 2009-204343, for example.
The aforementioned Japanese Patent Laying-Open No. 2009-204343 discloses a three-dimensional shape measuring apparatus including a stripe pattern projection portion having a light source and a DMD (digital mirror device) configured to reflect light emitted from the light source and apply stripe pattern light with which information about the height of an inspection target portion can be acquired to the inspection target portion. This three-dimensional shape measuring apparatus includes an imaging portion imaging the inspection target portion with the stripe pattern light emitted from the stripe pattern projection portion. In this DMD, a plurality of mirrors are arranged, and the DMD is configured to apply the stripe pattern light to the inspection target portion by reflecting the light emitted from the light source. The DMD is conceivably arranged to be substantially perpendicular to the traveling direction of the stripe pattern light emitted from the stripe pattern projection portion. Details of the arrangement state of the plurality of mirrors in this DMD are unknown.
Furthermore, a DMD having a quadrilateral outer shape in which a plurality of mirrors are arranged in a lattice pattern (in a grid pattern) (hereinafter referred to as the DMD in the lattice pattern) is known in general. The plurality of mirrors of the DMD in the lattice pattern each are formed in a substantially quadrilateral shape and have swing axes configured to swing the mirrors at positions corresponding to diagonals of the substantially quadrilateral shapes. These swing axes are substantially parallel to each other and are inclined at about 45 degrees with respect to a side (edge) of the DMD. A light source and the DMD are arranged such that the traveling direction of light emitted from the light source is substantially orthogonal to the swing axes of the plurality of mirrors. Therefore, in a three-dimensional shape measuring apparatus employing the DMD in the lattice pattern, the light source must be arranged at a prescribed interval in an oblique direction with respect to a corner of the DMD having the quadrilateral outer shape in a plan view.
In the case where the conventional DMD in the lattice pattern (in the grid pattern) is applied to the three-dimensional shape measuring apparatus described in the aforementioned Japanese Patent Laying-Open No. 2009-204343, however, the light source must be arranged at the prescribed interval in the oblique direction with respect to the corner of the DMD having the quadrilateral outer shape in the plan view, as hereinabove described, whereby the light source protrudes from the installation width of the DMD having the quadrilateral outer shape in the plan view. Consequently, the external dimension of the stripe pattern projection portion (light source unit) including the light source and the DMD is disadvantageously enlarged.